Multiple passage irrigation conduits typically include at least two tubes, one of which is adapted to be coupled to a source of water under pressure. A series of transfer passages pass water from the first tube to the second tube and discharge orifices allow the water to pass from the second tube to the environment. A drip irrigation conduit of this type is shown in Mock Pat. No. 3,903,929. If more than two tubes are used, the discharge orifices of the second tube pass the water into the third tube and so on until the final tube passes the water to the environment.
One advantage of a multiple passage drip irrigation conduit is that the multiple passages facilitate pressure reduction of the water. This assures that the water will pass from the drip irrigation conduit to the environment at the desired slow drip or trickle rate. Pressure reduction can be obtained in different ways, including appropriately sizing the total area of the transfer passage and the total area of the discharge orifices or by using a capillary tube or restricted orifices which present sufficient friction to fluid flow so as to provide the desired slow drip rate.
Although multiple passage drip irrigation conduits have numerous advantages, some difficulty has been experienced with the blockage of the transfer passages. One reason for this is that the transfer passages of the prior art must be of relatively small diameter in order to provide the desired pressure drop.